Recent advances in processing equipment and technology and a more stringent requirement on substrate cleanliness have directed renewed focus at the area of vapor phase wafer processing techniques. In particular, vapor phase hydrogen fluoride has been used in oxide etching and native oxide removal applications. Other applications of the vapor phase processing technique are also eagerly sought by the semiconductor processing industry.
In a typical wafer manufacturing process, a two-step oxide strip method is used prior to the formation of the gate oxide. This conventional two-step method consists of an aqueous hydrogen fluoride strip and a conventional wet clean. The latter is a sequence of known cleaning and rinsing steps based on solutions of HCl/H.sub.2 O.sub.2 and NH.sub.4 OH/H.sub.2 O.sub.2.
Accordingly, it has become desirable to apply the vapor phase processing technology to replace the conventional two-step cleaning method and achieve better wafer cleaning with increased oxide lifetime and other device characteristics.